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Megalosaurus
Megalosaurus (meaning "Great Lizard") is a genus of large meat-eating theropod dinosaurs of the Middle Juassic period (Bathonian stage, 166 million years ago) of Europe (Southern England, France, Portugal). It is significant as the first genus of dinosaur (outside of birds) to be described and named. Discovery Megalosaurus may have been the first dinosaur to be described in the scientific literature. Part of a bone was recovered from a limestone quarry at Cornwell near Chipping Norton, Oxfordshire, England in 1676. The fragment was sent to Robert Plot, Professor of Chemistry at the University of Oxford and first curator of the Ashmolean Museum, who published a description in his Natural History of Oxfordshire in 1676. He correctly identified the bone as the lower extremity of the femur of a large animal and he recognized that it was too large to belong to any known species. He therefore concluded it to be the thigh bone of a giant human, such as those mentioned in the Bible. The bone has since been lost but the illustration is detailed enough that some have since identified it as that of Megalosaurus. The Cornwell bone was described again by Richard Brokes in 1763. He called it "Scrotum humanum," while comparing its appearance to a pair of human testicles. The label was not considered to be a proper Linnaean "name" for the animal in question at the time, and was not used in subsequent literature. Technically, though, the name was published after the advent of binomial nomenclature, and so if it was truly intended to represent the establishment of a new genus it would have priority over Megalosaurus. However, the rules of the ICZN state that if a name has never been considered valid after 1899, it could be removed from competition for priority, becoming a nomen oblitum (forgotten name), while the junior synonym (in this case Megalosaurus bucklandi) could be made a nomen protectum (protected name). In the early 1990s, W.A.S. Sarjeant submitted a petition to the ICZN to formally suppress the genus name Scrotum in favor of Megalosaurus. The Executive Secretary of the ICZN at the time, P.K. Tubbs, rejected the petition, concluding that the term "Scrotum humanum", published merely as a label for an illustration, did not constitute the valid creation of a new name, and stated that there was no evidence it was ever intended as such. Furthermore, the partial femur was too incomplete to definitely be referred to Megalosaurus and not a different, contemporary theropod. Description Since those first finds, many other Megalosaurus bones have been recovered but still no complete skeleton has been found. Therefore, the details of its physical appearance cannot be certain. However, a full description of all known material was recently published. Early reconstructions In 1852, Benjamin Waterhouse Hawkins was commissioned to build a model of Megalosaurus for the exhibition of dinosaurs at the Crystal Palace in Sydenham, where it remains to this day. Early paleontologists, never having seen such a creature before, reconstructed it like the dragons of popular mythology, with a huge head and walking on all fours. The hump on the back of the sculpture in Crystal Palace and other restorations from the 1800s was based on the material now referred to as Becklespinax. It was not until the middle of the nineteenth century, when other theropods began to be discovered in North America, that a more accurate picture was developed. Some confusion still exists, for at one time, all theropods from Europe were given the title Megalosaurus. Since then, these have mostly been reclassified. For further confusion, the most reproduced anatomy diagram of a Megalosaurus' skeleton was produced before any vertebrae had been recovered. While drawing it, Friedrich von Huene of the University of Tubingen, Germany, instead used the backbones of Altispinax, a mysterious big theropod known from high-spined dorsal vertebrae and at times classified as a spinosaur. Hence, many later drawings, based on his original, show Megalosaurus with a deep spinal ridge or even a small sail, like that of Spinosaurus. Modern reconstructions Megalosaurus had a relatively large head and its teeth were those of a carnivore.However, the long tail would have balanced the body and head and so Megalosaurus is now restored as bipedal like all other theropods—about 9 meters in length. The structure of the cervial vertebrae suggests that its neck would have been very flexible. To support its weight of around one tonne, the legs were large and muscular. Like most theropods, it had three forward-facing toes and a hallux. Its forelimbs were small - although not proportionally as small as those of later theropods like Tyrannosaurus - and probably had three or four digits. Living in what is now Europe, during the Jurassic Period (181 to 169 million years ago), Megalosaurus may have hunted stegosaurs and sauopods. Repeated descriptions of Megalosaurus hunting Iguanodon (another of the earliest dinosaurs named) through the forests that then covered the continent are probably inaccurate, because Iguanodon skeletons are found in much younger Early Cretaceous formations. No fossils assignable to Megalosaurus have been discovered in Africa, contrary to some outdated dinosaur books. Classification For decades after its discovery, Megalosaurus was viewed by many researchers as a definitive or typical large carnivorous dinosaur. It has also historically been a Wastebasket taxon, and many large carnivorous dinosaurs from Europe and elsewhere were referred to the genus without justification. This began to change in the 20th Century, when scientists such as von Huene suggested that the genus should be restricted to the fossils found in the original Stonesfield Slate quarry, and this was followed by most later researchers. However, even further taxonomic revision began in the late 20th and early 21st Centuries, in which researchers such as Allain and Chure showed that the Stonesfield Slate fossils probably belonged to several, possibly unrelated, species of theropod dinosaur. Further research confirmed this hypothesis, and the genus Megalosaurus and species M. bucklandii became generally regarded as applying only to the type specimen, specifically to the species that produced the lower jaw. Furthermore, several researchers failed to find any characteristics in the jaw that could be used to distinguish Megalosaurus from its relatives, and many began to regard it as a nomen dubium. However, a comprehensive study by Benson and colleagues in 2008, and several related analyses published in subsequent years, overturned the previous consensus by identifying several apomorphies, or distinguishing characteristics, in the lower jaw that could be used to separate Megalosaurus from other megalosaurids. Category:Dinosaurs Category:Extinct in Britain Category:Saurischian Category:Vertebrates Category:Chordata Category:Extinct Reptiles and Amphibians